Podcast: Explaining Pratt & Whitney's Durability Problem

Listen in as Aviation Week's brains trust breaks down what's behind the grounding of scores of airplanes and how Pratt is working to fix it.

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• Pratt Ramps Up Overhaul Capacity Amid Engine-Reliability Struggles
• India’s Go First Attributes Bankruptcy To Engine-Related Groundings
• Engine Shortage Forces Lufthansa Group To Ground A Third Of Its A220s

Rush Transcript

Joe Anselmo: 

Welcome to this week's Check 6 podcast. I'm Joe Anselmo, Aviation Week's editorial director.

Airlines grappling with engine reliability issues may have to put up with delays in getting parts or airworthy engines for several more years, Aviation Week's Sean Broderick and Guy Norris report. Central to this story is Pratt & Whitney's PW1000G family geared turbo fan engine, or GTF. It has proven to be less durable than projected, swamping the company's overhaul capacity and forcing numerous airlines to ground their Airbus A320 Neo family and A220 aircraft. In fact, one airline in India claims the engine problems have forced it into bankruptcy. Pratt is expanding shop capacity and working on upgrades to make the engines more reliable, but by its own admission is not where it needs to be.

Airlines flying CFM LEAP engines are also seeing issues, but those are far less widespread. Joining me to break this all down are Sean Broderick and Guy Norris. And rounding out the brain trust is the numbers guy, Daniel Williams, our manager of civil fleet, flight and forecast data.

So Sean, we've been talking a lot over the last year about Airbus and Boeing having delays in delivering new aircraft because of engine shortages. That's not what we're talking about here. These are in-service aircraft where they have to be taken out of service because the engines aren't holding up as long as they should between maintenance rounds, right?

Sean Broderick: 

Yeah, that's absolutely right. I mean I think it's fair to say that the geared turbofan has had durability issues as opposed to reliability issues. It's had durability issues since its entry into service in 2016 and as we'll talk about a little bit more in depth here in a few minutes, it is not the geared feature for the turbofan that is having issues. That, which was thought to be the most complicated feature of the design, has done well. It's been a series of other things that is causing the engines to come off wing early.

Pratt has been chasing several specific issues, again, which we'll get into more here in a little bit. The problem now is that the number of engines in service and the timeline on which these durability issues begin to rear their ugly heads, perhaps at a point where it can't keep up with demand to fix the engines that are having problems, and then of course can't replace every problem engine with a new engine because of Airbus' ramp up plans and production rates.

A rough look at the numbers of deliveries, started at about 100 in 2016. These are engines. Up closer to 200 in 2017, 450 in 2018, about 650 in 2019. So you have a ramp up and then it was in the 500s the last three years, almost 600 last year. That branch of early engines is hitting a point where they need fixes and the MRO capacity, although Pratt is building it, can't keep up. There are some parts issues as well. It's unclear the mix of MRO capacity versus parts, but the result is we have scores of airplanes that are grounded waiting for engines and it's only going to get worse it looks like for at least the next year or possibly two.

Joe Anselmo:       

Dan Williams, I suspect Sean was just citing some of your numbers there, but let's bring you into this. Can you give us a sense of which airlines are most affected and the scope of this problem? How big is it?

Dan Williams:       

Yeah, thank you very much. I went away and, being the numbers guy, I wanted to live up to my name. So studying the numbers, if you look at the two bigger operators affected and well publicized, certainly, are GoAir and IndiGo. IndiGo have nearly 140 aircraft that are powered by GTFs. However, about a third of those are stored or underutilized, so they're not flying day in, day out. They may be only flying one or two days out of the previous seven or have been on the ground for seven-plus days as well.

GoAir, which was the airline that you were alluding to before, are putting a huge amount of responsibility at Pratt's door for where they currently stand. They've got about two thirds of their fleet parked up. Coincidentally, both of those operate in a relatively harsh environment for engines. There are a couple of areas around the globe where they are harsh environments and things like particle ingestion into the engine.

So sand, as an example, is something that adds to what Sean was talking about, it's a durability rather than a reliability. It's parts wearing sooner rather than necessarily parts failing. They're two very different aspects of it. And these two Indian airlines are not exclusively the only ones affected. AirBaltic for example, they've got about nearly a third of their fleet, their A220s, which is also powered by the GTF, on the ground as well. And it's quite interesting that they're leasing in supplementary aircraft, older A320s, to run their fleet while simultaneously leasing out their A220s to other operators like Swiss, who are another affected operator because they have A220s as well.

So it's not exclusive to these Indian airlines, however it is felt across all sectors of the market. And just using some of our other flight tracking data, for example, in April of 2023, aircraft that are powered by GTF spent just over 10,000 days on the ground. They did spend nearly 38,000 days, when you roll them all up, flying. So comparatively, it's not a huge number, however it is a significant amount considering 10,000 days on the ground for an aircraft -- you're not making money whilst an aircraft's sat on the ground.

Joe Anselmo:           

Guy Norris, some background for some of our younger listeners; the GTF has been a huge success for Pratt & Whitney. It really revived the company's fortunes in the commercial aviation market and has just been a gangbuster for Pratt. They are working on fixes to this problem, right? So the engines last longer between maintenance rounds?

Guy Norris:         

Yeah. Thanks, Joe. You saw to remind people about what goes on with the GTF. As Sean alluded to, the gear at the center of the concept, which really allows the fan to run at a much lower speed and the turbine to run at a higher speed, that's been bulletproof throughout the whole thing. I mean, Pratt did a great job in making sure that was not going to be the problem. But the other aspect about this advanced engine, like all the new generation engines, is that they have a much higher overall pressure ratio and run at a much higher temperature. And that's all aimed at fuel efficiency, because the hotter you can run these things, the more fuel efficient you get. The downside of that, as we're now discovering of course, is durability. The problem crops up in the hottest part of the engine, as you'd expect, around the combustor and the turbine section usually.

In this case, Pratt's problem really is focused on the combustor. And just to go back a little bit, something Sean said, to be honest, the GTF did have a few, pretty well known in fact, in service teething issues. And he's right, the reliability side is mostly behind them, it's now durability. We just have to remember that. So just to look at what the problem is. So if you look at a combustor, the combustor is remember where the air and the fuel are mixed, where it's the bang part of the suck, squeeze, bang cycle in an engine. So the combustor is where you get this terrific temperature buildup and the way that you handle that, as far as not burning the engine up itself, is you have generally two layers. One's called an effusion layer. It's basically a cooling plate and the other one is an impingement plate. These are two parallel layers.

So between those you have all these little holes for cooling, because what you have to do is obviously transfer the heat in a good way out of the combustor, and the cooling hole's the way to do this. Now, as Dan mentioned, a lot of these, particularly the A320 Neo families, have been operating in polluted environments or where you get a lot of dust in the air and dust gets stuck in these little tiny holes. It's just a problem of physics essentially. So when you get blockage in these holes, you can't get that heat transfer going and that's the problem.

So all of a sudden your durability starts to go through the floor. You cannot keep these things in service. And every time you inspect an engine, every time there's an indication in the cockpit of a temperature increase, you've got to go out there, you've got to do a borescope, and as soon as you start to see degradation in the combustor, either in the lining of that combustor, which is what you see when you look through the borescope, you know that you've either got to do a repair or you've got to take the thing out. And that's been the problem.

So the whole engine has to come off. You can't do this on wing, it's just one of those issues. So Pratt's dealing with it in several ways; one is they're basically redesigning -- they've gradually improved the positioning and the location of the holes to alleviate the blockage problem. They've worked their way through now four generations of combustor designs. A through C, they always had the problem.

Finally, with D, they fixed it in terms of the position holes. They're still getting issues because they're not quite there yet with it. So at the moment they're working on this new combustor version called the D.2. And that's going to be rolled in pretty well in the next upgrade. In the meantime, as Sean mentioned, you've got all of these engines out there which are desperately needing some retrofit. So what happens next is the Advantage program, which is the next generation of GTF, this deals with all of the problems including the earlier reliability issues. But of course that's not going to be introduced until next year. But they do have this long-term vision to get to solve the issue.

And the last thing I'll just mention, which is connected to the supply problem of components for these improved engines, is that the Tier One suppliers have really got their act together finally, and I think we've talked about this in previous podcasts. The supply chain is getting better as we've seen and deliveries are being made to the OEMs for the airframers. But if you drill down any distance or any sort of length into that supply chain, Tier Two and below is where the problems are still existent.

In the case of the Pratt engine, one of the big problems they have now is, remember last year it was to do with Precision Castparts and the big casting parts? Now it's down to the tier two, tier three people who are precision welders. When you put these combustors together, you've got to integrate hot and cold sections. Precision welding is a key skill and right now they're finding a shortage of these people because during the pandemic they all went off and became workers in the utility industry. They all could make as much money, more money in fact, helping people with fixing their plumbing than they could working on precision welding in a mom and pop shop. So that's a big issue down the stream where they've got to really address.

Joe Anselmo:    

Sean, I wanted to ask you about this Indian ultra low-cost carrier, Go First Airlines. You wrote that they have 50 Pratt powered, A320 Neos, 29 of those are on the ground, and they're claiming that this issue has caused them to go bankrupt. I've never seen an airline go bankrupt because of something an OEM did. Are you buying that?

Sean Broderick:   

Well, the durability issues with these engines certainly didn't help. As Dan mentioned, if you're not flying the airplane, you're not making money. That said, I think, and this is important to note this is Adrian Schofield's reporting out of our Asia-Pac bureau, so he's far more the expert on this vis-a-vis me, but I think there were some payment issues between the airline and the OEM that maybe the airline did not cite when it listed the reasons for its bankruptcy. They certainly didn't get the engines they needed, but they are not alone. And Dan has a list of, I don't know how many, dozens of airlines with airplanes on the ground that would love to see Pratt pull engines off the line and solve their problems. So Go First maybe arguably the most affected I suppose. But any airline that goes bankrupt, you're going to have more than one problem. So I think it was convenient for them to label Pratt on that.

Dan Williams:    

Yeah, just to add to what Sean said, it's a very good point. GoAir have about 50 aircraft and about nearly two thirds of them sat on the ground. Let's put it in context; Spirit. U.S.-based operator, plenty of Neos, nearly 80 aircraft and they've got three or four or five on the ground. So they are a similar sized fleet to GoAir, slightly bigger. Obviously operating in very different environments, which I think this plays a key factor into this durability issue. And I think this is a multitude of reasons where we are today. Like Guy said, there's a supply chain issue, so there's issues getting those parts to turn those engine rounds quickly.

There's an issue with having spare engines available because of the durability issue. All the spare engines have been utilized and used up, so that constant switching and changing of those spare engines, they've just run out of spare engines. If there was another couple of dozen spare engines that GoAir had then I think they will be in a different situation. And to add to the GoAir, I think that the engines is the straw that broke the camel's back. I don't think it's completely all the reasons why where they are today. However, it might have just been that final tipping point.

Guy Norris:         

And just to add to what Dan was saying, I think from Pratt's perspective, I think they feel like they've been hung out to dry here. I mean, they basically say on the record that any claims that or allegation that Go First is making about them being responsible for the financial condition that they find themselves in is totally without merit. And if you look behind the scenes, some of our sources have told us that, basically, this airline stopped paying Pratt for its services as far back as 2017 and that Pratt wanted to obviously help it out and continue its association with this operator. But by 2021, in the middle of the pandemic, so we hear, things got so bad that the engine maker wanted to sort of say, "Look, you got to step up here and make at least a token payment," which apparently did happen in late '22.

But at that stage the airline said, "We need the engines right now." So Pratt apparently did ship 17 engines, but GoAir turned around and said that they needed 50 more. And by then there was just literally no way this could be done because of the production ramp up and the situations that we've already discussed. So I think just the last thing I was going to say at this point is what happens next? Because it's not just Go. All of these operators that Dan's been talking about, all the numbers out there, where are these engines going to come from and what's it going to mean for Airbus, frankly?

Joe Anselmo:          

Sean, on the recent earnings call of Pratt's parent company, Raytheon Technologies, Greg Hayes, the chairman and CEO of the company, talked about transitioning to this new Advantage system. Tell us what the Advantage system is and how long that's going to take.

Sean Broderick:   

I'll give Guy the honor of doing the technical breakdown on the Advantage because he's written about this, but a couple of important notes on that; first, this is a change on the production line and the goal, I believe, is to transition to all Advantage by somewhere around end of 2025, 2026. So in theory, all the engines coming off the line at that point will not have any of these issues. Now one important point, that I believe Guy will correct me if I'm wrong, you can't intermix. The D standard combustor, the block D standard combustor, is retrofittable on every engine that's out there. I believe. And that's one of the goals is if they could instantly put the block D into every engine, they'd have this problem solved. The advantage though is a different build standard and you cannot intermix Advantage engines and pre-Advantage engines. Guy, did I get that right on the Advantage and the intermixing?

Guy Norris:

Essentially the new standard engine will be interchangeable actually with the current production version. Pratt basically says the new variant can also be paired with the existing 1100G. So if you intermix the cooler-running Advantage with the current engine at de-rated thrust settings, you'll also increase the time on wing, which is another part of reducing the maintenance costs and getting that durability up. From what I understand though, you can't actually obviously interchange the combustors because of the different designs, but certainly an engine as a whole you can intermix.

Sean Broderick:  

Ah, well, I'm glad you're here to back me up.

Guy Norris:        

You're welcome.

Sean Broderick:        

Or bail me out, as the case may be. So they're expanding their MRO network. I’ll talk about that real quick. About four years ago they had four or five service centers that could handle any GTF work. There was supposed to be a lot back then, but turns out that there was. They're now up to 12 and they're supposed to have about 19 online by 2025. Now a lot of this will handle expected demand that was forecasted long ago when the engines need their first overhauls. It's going to be important for Pratt to have the partners that they have handling that so they can focus them, and MTU and a few of these others, can focus on doing these hospital type visits or these block D retrofits. But again, 2025 is a long time down the road if you're Spirit and it's too late if you're a GoAir, or a Go First, to solve these current problems.

Guy Norris:   

And just to follow there, Sean, just to remind people that the Advantage really is designed to correct all of the issues they've had and bring the engine up to the durability standards that people would like to see, and it basically is focused on increasing the air flow through the core. It's modifications to the three-stage low pressure compressor that boost the available thrust, and at the same time it provides a 1% fuel consumption gain or benefit. So the package actually rematches the flow of the turbines by changing the frontal area of the two-stage high pressure turbine and the three-stage LPT. So combining that with improvements to the combustor, it's a heck of a big change. It's much more than you'd imagine and it's really genuinely a second generation engine. And it's due to start rolling down the line, I believe, later this year. And of course get into service, assuming certification goes okay, next year.

Joe Anselmo:   

Dan Williams, we were all talking a couple of days ago offline about this and I did note at the beginning of this podcast that this is a problem with existing in-service aircraft, but you prepare our forecasts for deliveries. Is this issue going to affect the production of new airplanes and delivery of new air airplanes? Is it going to slow it down?

Dan Williams:   

Yeah, I think it's well publicized that Pratt have said that we're not going to see any relief in this until the next calendar year. And when you look at the platforms that they're on, the A320 Neo family, well about 45% of those are powered by Pratt. The other 55 are powered by LEAP. So those LEAP powered A320 Neos, they should be just fine. So maybe what'll happen is near term, Airbus can work with their LEAP purchase customers, assuming CFM can produce enough engines for them with the supply chain issues, the workforce issues and so on and so forth, these are existential issues that are affecting everybody, then it may not affect them too much.

However, when you look at those production runs that rely exclusively on the GTF, the A220 and the Embraer E2, then that will have impact with them. But again, that's not necessarily exclusively because of the durability. That's in part because of supply chain, workforce, et cetera. So it will have an impact through till 2024 definitely. But Airbus could be potentially clever with their customers and pivot more towards the LEAP if CFM can keep up the rates that are required as well.

Joe Anselmo:           

Okay, well, on that note, we will wrap this up. I'm sure we'll all be back to talk about it more as this is an ongoing problem. It's certainly not going to go away anytime soon. But for now, that is a wrap for this week's Check 6 podcast. A special thanks to our podcast editor in London, Guy Ferneyhough.

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